Eight supermarkets have agreed to a set of principles following concerns over special offers and promotions for food and drink, the Office of Fair Trading (OFT) has announced.
Aldi, The Co-operative, Lidl, Marks & Spencer, Morrisons, Sainsbury's, Tesco and Waitrose have agreed to adopt the principles to ensure promotions are "fair and meaningful" for customers.
They cover claims such as "Was £3, Now £2" or "Half Price", which must now only be offered for the same or less time than the product was initially sold at the higher price. The supermarkets have also agreed not to artificially inflate prices to make a later "discount" look more attractive.
Pre-printed claims on packs, such as "Bigger Pack, Better Value", must be true, and there should not be a cheaper way of buying the same volume of the product elsewhere in the same store, even if there is a promotion on smaller packs of the same item.
The OFT said it launched its investigation into the sector to consider concerns that shoppers could be confused by the way prices are displayed, advertised and promoted. It did not find that the supermarkets had breached the law or were engaging in misleading promotional practices but did find "what appeared to be inconsistency in the way the law was being interpreted and applied", it said.
OFT chief executive Clive Maxwell said: "Household budgets across the country are under pressure and shoppers should be able to trust that special offers and promotions really are bargains.
"Prices and promotions need to be fair and meaningful so shoppers can make the right decisions. Nowhere is this more important than during regular shopping for groceries, which accounts for 44% of household spending.
"Our principles taken together with previous guidance provide supermarkets with a clear benchmark for how they should be operating so that their food and drink promotions reflect the spirit as well as the letter of the law. We are pleased that supermarkets have engaged constructively throughout our investigation and we will keep a watching brief on promotional practices in this sector."
Which? executive director Richard Lloyd said: "We now want the retailers to go further and make a stronger commitment to fair treatment of their customers, so that as well as scrapping misleading promotions, they ensure busy shoppers see clear, consistent unit pricing with real bargains that are easy to spot at a glance.
"When household budgets are squeezed and food prices are one of people's top financial worries, it's unacceptable that shoppers are confused into thinking that they're getting a good deal when that might not be the case. Regulators should be prepared to take enforcement action against traders found breaking the rules."